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arXiv · 2608.13205

HPSD: Hybrid-Policy Self-Distillation for Text-Image-to-Video Diffusion Models

Jiazi Bu·Pengyang Ling·Yujie Zhou·Yibin Wang·Yuhang Zang·Xuanlang Dai·Shengyuan Ding·Tianyi Wei·Xiaohang Zhan·Jiaqi Wang·Tong Wu·Dahua Lin·Xingang Pan
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Abstract

Text-Image-to-Video (TI2V) models are an emerging unified architecture, where a single model simultaneously supports text-to-video (T2V) and image-to-video (I2V) generation. Given a high-quality first frame or a detailed textual prompt, TI2V models unlock substantially better visual quality than their T2V mode, raising a natural question: can the capability elicited by such privileged conditions be internalized into the model's own base generation ability? A common approach toward this goal is model self-distillation. However, the most straightforward solution, supervised fine-tuning, follows an off-policy strategy: its supervision is confined to teacher-generated endpoints from a fixed offline distribution rather than student-visited states, lacking precise correction tailored to the evolving policy. Recent on-policy distillation methods instead suffer from condition-state mismatch, where supervision is steered toward the given first frame instead of the student's actual content, misleading the correction. To achieve self-distillation that absorbs the teacher's privileged prior while retaining precise policy correction, in this work, we propose Hybrid-Policy Self-Distillation (HPSD), a novel self-distillation framework where a single TI2V model acts as both teacher and student under different conditions: the teacher operates in TI2V mode with a high-quality first frame and an enhanced prompt, while the student runs in the base T2V mode with only the vanilla prompt. Specifically, the student inherits off-policy teacher trajectory points as anchors, locally refines them toward its own policy, and finally receives velocity-level supervision on these self-generated roll-outs. Extensive experiments demonstrate that HPSD significantly improves T2V performance while also delivering notable TI2V gains, effectively strengthening the model's base generation ability.

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Jiazi Bu, Pengyang Ling, Yujie Zhou, Yibin Wang, Yuhang Zang, Xuanlang Dai, Shengyuan Ding, Tianyi Wei, Xiaohang Zhan, Jiaqi Wang, Tong Wu, Dahua Lin, Xingang Pan. 2026-08-13. HPSD: Hybrid-Policy Self-Distillation for Text-Image-to-Video Diffusion Models. https://arxiv.org/abs/2608.13205

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